Imaging system for vehicle

ABSTRACT

An imaging system for a vehicle includes an imaging array sensor and a control. The imaging array sensor comprises a plurality of photo-sensing pixels and is disposed at an exterior rearview mirror assembly at a side of the vehicle with a field of view exterior of the vehicle. The imaging array sensor is operable to capture an image exterior of the vehicle. The control may process the captured images and may determine that the imaging array sensor is misaligned when the imaging array sensor is disposed at the exterior rearview mirror assembly at the side of the vehicle. The control, responsive to a determination of misalignment of the imaging array sensor, may at least partially compensate for the determined misalignment of the imaging array sensor.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/764,355, filed Apr. 21, 2010, now U.S. Pat. No. 7,877,175,which is a continuation of U.S. patent application Ser. No. 11/315,675,filed Dec. 22, 2005, now U.S. Pat. No. 7,720,580, which claims benefitof U.S. provisional application Ser. No. 60/638,687, filed Dec. 23,2004, which is hereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to vision or imaging systems forvehicles and is related to object detection systems and, moreparticularly, to imaging systems which are operable to determine if avehicle or object of interest is adjacent to, forward of or rearward ofthe subject vehicle to assist the driver in changing lanes or parkingthe vehicle. The present invention also relates generally to a lanedeparture warning system for a vehicle

BACKGROUND OF THE INVENTION

Many lane change aid/side object detection/lane departure warningdevices or systems and the like have been proposed which are operable todetect a vehicle or other object that is present next to, ahead of orrearward of the equipped vehicle or in an adjacent lane with respect tothe equipped vehicle. Such systems typically utilize statisticalmethodologies to statistically analyze the images captured by a cameraor sensor at the vehicle to estimate whether a vehicle or other objectis adjacent to the equipped vehicle. Because such systems typically usestatistical methodologies to determine a likelihood or probability thata detected object is a vehicle, and for other reasons, the systems maygenerate false positive detections, where the system indicates that avehicle is adjacent to, forward of or rearward of the subject vehiclewhen there is no vehicle adjacent to, forward of or rearward of thesubject vehicle, or false negative detections, where the system, forexample, indicates that there is no vehicle adjacent to the subjectvehicle when there actually is a vehicle in the adjacent lane.

Such known and proposed systems are operable to statistically analyzesubstantially all of the pixels in a pixelated image as captured by apixelated image capture device or camera. Also, such systems may utilizealgorithmic means, such as flow algorithms or the like, to tracksubstantially each pixel or most portions of the image to determine howsubstantially each pixel or most portions of the image has changed fromone frame to the next. Such frame by frame flow algorithms and systemsmay not be able to track a vehicle which is moving at generally the samespeed as the equipped vehicle, because there may be little or norelative movement between the vehicles and, consequently, little or nochange from one frame to the next. Because the systems may thussubstantially continuously analyze substantially every pixel forsubstantially every frame captured and track such pixels and frames fromone frame to the next, such systems may require expensive processingcontrols and computationally expensive software to continuously handleand process substantially all of the data from substantially all of thepixels in substantially each captured image or frame.

Many automotive lane departure warning (LDW) systems (also known as runoff road warning systems) are being developed and implemented onvehicles today. These systems warn a driver of a vehicle when theirvehicle crosses the road's land markings or when there is a cleartrajectory indicating they will imminently do so. The warnings aretypically not activated if the corresponding turn signal is on, as thisimplies the driver intends to make a lane change maneuver. Additionally,the warning systems may be deactivated below a certain vehicle speed.The driver interface for these systems may be in the form of a visualwarning (such as an indicator light) and/or an audible warning(typically a rumble strip sound). One application warns a driver with anindicator light if the vehicle tire is crossing the lane marker and noother vehicle is detected in the driver's corresponding blind spot;and/or further warns the driver with an audible warning if the vehicleis crossing into the adjacent lane and there is a vehicle detected inthe driver's blind spot.

There is concern that the current systems will be more of a driverannoyance or distraction than will be acceptable by the consumer market.Using the turn signal as the principle means of establishing to thewarning system that the maneuver is intentional does not reflect typicaldriving patterns and, thus, many intended maneuvers will cause awarning. As a driver gets annoyed by warnings during intended maneuvers,the driver will likely begin to ignore the warnings, which may result inan accident when the warning is appropriate.

Therefore, there is a need in the art for an object detection system,such as a blind spot detection system or lane change assist system orlane departure warning system or the like, which overcomes the shortcomings of the prior art.

SUMMARY OF THE INVENTION

The present invention is intended to provide an object detection system,such as a blind spot detection system, a lane change assist or aidsystem or device, a lane departure warning system, a side objectdetection system, a reverse park aid system, a forward park aid system,a forward, sideward or rearward collision avoidance system, an adaptivecruise control system, a passive steering system or the like, which isoperable to detect and/or identify a vehicle or other object of interestat the side, front or rear of the vehicle equipped with the objectdetection system. The object detection system of the present invention,such as for a lane change assist system, utilizes an edge detectionalgorithm to detect edges of objects in the captured images anddetermines if a vehicle is present in a lane adjacent to the equipped orsubject vehicle in response to various characteristics of the detectededges, such as the size, location, distance, intensity, relative speedand/or the like. The system processes a subset of the image datacaptured which is representative of a target zone or area of interest ofthe scene within the field of view of the imaging system where a vehicleor object of interest is likely to be present. The system processes thedetected edges within the image data subset to determine if theycorrespond with physical characteristics of vehicles and other objectsto determine whether the detected edge or edges is/are part of a vehicleor a significant edge or object at or toward the subject vehicle. Thesystem utilizes various filtering mechanisms, such as algorithmsexecuted in software by a system microprocessor, to substantiallyeliminate or substantially ignore edges or pixels that are not or cannotbe indicative of a vehicle or significant object to reduce theprocessing requirements and to reduce the possibility of false positivesignals.

The object detection system of the present invention may capture imagesat a side of the vehicle and may process various windows of the imagesto detect a vehicle in the adjacent lane or other object, such as abicycle, in the adjacent lane. The system may adjust the imageprocessing to account for misalignment of the camera at the side of thevehicle. The system may adjust the area or zone of interest in responseto a turning of the vehicle's wheels, such as when the vehicle isturning or curving along a curve in the road. The system may distinguishbetween vehicles or other objects and shadows of objects/vehicles sothat a shadow of a vehicle two lanes over may not be considered avehicle in the adjacent lane. The system may switch between daytime andnighttime algorithms and may be operable to detect headlamps of vehiclesin the adjacent lane.

According to an aspect of the present invention, an imaging system for avehicle includes an imaging array sensor and a control. The image arraysensor comprises a plurality of photo-sensing pixels and is positionedat the vehicle with a field of view exteriorly of the vehicle. Theimaging array sensor is operable to capture an image of a sceneoccurring exteriorly of the vehicle. The captured image comprises animage data set representative of the exterior scene. The controlalgorithmically processes the image data set to a reduced image data setof the image data set. The control processes the reduced image data setto extract information from the reduced image data set. The controlselects the reduced image data set based on a steering angle of thevehicle.

Optionally, the control may process the reduced image data set with anedge detection algorithm to extract information from the reduced imagedata set. The image sensor may be one of (a) part of an exteriorrearview mirror assembly of the vehicle and with a field of view atleast partially sideward of the vehicle, and (b) at an upper windshieldarea and behind the windshield of the vehicle and with a field of viewforward and through the windshield (such as at an area that is cleanedby the windshield wiper or wipers of the vehicle when the windshieldwipers are activated). Optionally, the image sensor may be part of anexterior rearview mirror assembly of the vehicle and with a field ofview at least partially sideward of the vehicle, wherein the imagingsystem comprises a side object detection system for detecting objects ata side of the vehicle. Optionally, the image sensor may be at an upperwindshield area and behind the windshield of the vehicle and with afield of view forward and through the windshield, wherein the imagingsystem comprises a lane departure warning system.

Therefore, the present invention provides an imaging system for use asor in association with a side object detection system and/or a lanedeparture warning system. The system is operable to process capturedimage data of a scene occurring exteriorly and along one or both sidesof the vehicle to determine if a target vehicle or object of interest islocated at or in the lane adjacent to the subject or host vehicle. Theimaging system of the present invention may process zones or areas ofinterest in the captured images and may adjust processing to accommodateany misalignment of the camera that may occur during installation of thecamera at the side of the vehicle. The side object detection system mayalso select or adjust the image processing to select/adjust the areas ofinterest, such as in response to a steering angle of the vehicle, suchas a turning of the wheels of the vehicle, so that the zone or area isadapted for the turning of the subject vehicle. The imaging system ofthe present invention thus provides enhanced processing of capturedimages to provide the desired function of the imaging system orassociated control or control system or alert system.

These and other objects, advantages, purposes and features of thepresent invention will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a vehicle incorporating the objectdetection system of the present invention;

FIG. 2 is a representation of a captured image of a side area of avehicle as captured by an imaging sensor in accordance with the presentinvention;

FIGS. 3A-C are schematics of the captured image of FIG. 2 showing theadjustments that may be made to the image processing to account formisalignment of the image sensor;

FIG. 4 is a schematic showing an adjustment of the area of interest whenthe wheels of the subject vehicle are turned;

FIG. 5 is a plan view of one of the wheels of the subject vehicleshowing the angles of the wheel as it is turned;

FIGS. 6-9 are representations of captured images of the side area of thevehicle, showing how different shadows may be detected;

FIG. 10 is a schematic of the image processing windows useful inprocessing the captured images in accordance with the present invention;

FIG. 11 is a representation of a captured image of the side area of thevehicle, showing different processing windows used to detect the vehiclein the adjacent lane;

FIG. 12 is a plot of the gray level values of the rows of pixels as aresult of a wide line integration in accordance with the presentinvention;

FIG. 13 is a processing mask for processing the windows of the capturedimages using gradient calculations in accordance with the presentinvention;

FIG. 14 is a representation of a captured image showing the shadow ofthe vehicle in the area adjacent to the vehicle;

FIG. 15 is a process flow diagram showing the bicycle detection functionof the present invention; and

FIGS. 16-20 are representations of captured images of the side area ofthe subject vehicle, showing the headlight detection function of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and the illustrative embodiments depictedtherein, an object detection system or imaging system, such as a lanechange assist or aid system 10, is positioned at a vehicle 12 (such asat an exterior rearview mirror 12 a of a vehicle) and is operable tocapture an image of a scene occurring sidewardly and rearwardly at oralong one or both sides of vehicle 12 (FIG. 1). Lane change assistsystem 10 comprises an image capture device or sensor or camera 14,which captures an image of the scene occurring toward a respective sideof the vehicle 12, and a control 16, which processes the captured imageto determine whether another vehicle 18 is present at the side ofvehicle 12, as discussed below. Control 16 may be further operable toactivate a warning indicator or display or signal device to alert thedriver of vehicle 12 that another vehicle is present at the side ofvehicle 12. The warning or alert signal may be provided to the driver ofvehicle 12 in response to another vehicle being detected at the blindspot area (as shown in FIG. 1) and may only be provided when the driverof vehicle 12 actuates a turn signal toward that side or begins turningthe subject vehicle 12 toward that side to change lanes into the laneoccupied by the other detected vehicle 18. The control and imagingsystem may utilize aspects described in U.S. patent application Ser. No.10/427,051, filed Apr. 30, 2003 by Pawlicki et al. for OBJECT DETECTIONSYSTEM FOR VEHICLE, now U.S. Pat. No. 7,038,577, which is herebyincorporated herein by reference. Reference is made to U.S. patentapplication Ser. No. 10/427,051, for a discussion of image processingtechniques and control functions useful with the present invention.

Optionally, the imaging system and object detection system of thepresent invention may utilize aspects of the imaging systems ordetection systems of the types described in U.S. Pat. Nos. 5,929,786and/or 5,786,772, and/or U.S. patent application Ser. No. 10/427,051,filed Apr. 30, 2003 by Pawlicki et al. for OBJECT DETECTION SYSTEM FORVEHICLE, now U.S. Pat. No. 7,038,577; and/or Ser. No. 11/239,980, filedSep. 30, 2005 by Camilleri et al. for VISION SYSTEM FOR VEHICLE, nowU.S. Pat. No. 7,881,496, and/or U.S. provisional applications, Ser. No.60/628,709, filed Nov. 17, 2004 by Camilleri et al. for IMAGING ANDDISPLAY SYSTEM FOR VEHICLE; Ser. No. 60/614,644, filed Sep. 30, 2004;and/or Ser. No. 60/618,686, filed Oct. 14, 2004 by Laubinger for VEHICLEIMAGING SYSTEM, or of the reverse or backup aid systems, such asrearwardly directed vehicle vision systems utilizing principlesdisclosed in U.S. Pat. Nos. 5,550,677; 5,760,962; 5,670,935; 6,201,642;6,396,397; 6,498,620; 6,717,610 and/or 6,757,109, and/or U.S. patentapplication Ser. No. 10/418,486, filed Apr. 18, 2003 by McMahon et al.for VEHICLE IMAGING SYSTEM, now U.S. Pat. No. 7,005,974, or of automaticheadlamp controls, such as the types described in U.S. Pat. Nos.5,796,094 and/or 5,715,093; and/or U.S. patent application Ser. No.11/105,757, filed Apr. 14, 2005, now U.S. Pat. No. 7,526,103; and U.S.provisional applications, Ser. No. 60/607,963, filed Sep. 8, 2004 bySchofield for IMAGING SYSTEM FOR VEHICLE; and Ser. No. 60/562,480, filedApr. 15, 2004 by Schofield for IMAGING SYSTEM FOR VEHICLE, or of rainsensors, such as the types described in U.S. Pat. Nos. 6,250,148 and6,341,523, or of other imaging systems, such as the types described inU.S. Pat. Nos. 6,353,392 and 6,313,454, which may utilize variousimaging sensors or imaging array sensors or cameras or the like, such asa CMOS imaging array sensor, a CCD sensor or other sensors or the like,such as the types disclosed in commonly assigned, U.S. Pat. Nos.5,550,677; 5,760,962; 6,097,023 and 5,796,094, and U.S. patentapplication Ser. No. 09/441,341, filed Nov. 16, 1999 by Schofield et al.for VEHICLE HEADLIGHT CONTROL USING IMAGING SENSOR, now U.S. Pat. No.7,339,149, and/or PCT Application No. PCT/US2003/036177 filed Nov. 14,2003, published Jun. 3, 2004 as PCT Publication No. WO 2004/047421 A3,with all of the above referenced U.S. patents, patent applications andprovisional applications and PCT applications being commonly assignedand being hereby incorporated herein by reference.

The image sensor may be located at the vehicle so as to have a sidewardfield of view, such as at an exterior rearview mirror of the vehicle,such a generally or at least partially within an exterior rearviewmirror of the vehicle. For example, an image sensor may be locatedwithin an exterior rearview mirror assembly of the vehicle and may havea generally rearwardly and sidewardly field of view through atransflective reflective element of the exterior rearview mirrorassembly. In such an application, the image sensor may be incorporatedin or associated with a side object detection system that detectsobjects at a side or blind spot area of the controlled or subjectvehicle. Optionally, the image sensor may have a generally forward fieldof view to capture images of a scene occurring forwardly of the vehicle.The image sensor may be located within the vehicle cabin and rearward ofthe windshield so as to have a field of view forwardly and through thewindshield of the vehicle, preferably at a location that is cleaned bythe windshield wipers of the vehicle, such as at an interior rearviewmirror assembly of the vehicle or at an accessory module or windshieldelectronics module or the like. In such an application, the image sensormay be incorporated in or associated with a lane departure warningsystem that detects a departure of the controlled or subject vehiclefrom a lane as the vehicle travels along a road.

Camera Calibration:

In order to verify that the camera or imaging sensor is mounted at thevehicle (such as at an exterior portion of the vehicle) within a desiredtolerance limit so as to provide the desired field of view, the cameramay detect the side of the vehicle (shown at 30 in FIG. 2) and/or thedoor handle or handles (the front door handle is shown at 32 a in FIG.2, while the rear door handle is shown at 32 b in FIG. 2) of the vehicleand the control may confirm that they are in the expected location inthe captured images. If the control determines that the camera is notaligned or aimed at the desired location (such as by determining thatthe vehicle edge and/or door handle/handles are not at the expectedlocation), the control may adjust the image and/or image processing toaccount for any such misalignment of the camera. For example, the degreeof misalignment may be calculated, and the image processing may beadjusted or shifted and/or rotated to position the reference structureat the appropriate location in the captured images.

For example, the algorithm may function to preprocess the captured imageby a histogram equalization to improve the image contrast. The algorithmmay then process the captured images via an edge detection in the areaof interest to extract the expected edge of the vehicle (shown at 34 inFIG. 2). The algorithm may filter the image data to remove noise in theedge detected image. The algorithm may perform a coarse structurefitting (such as via a line fitting algorithm or contour fittingalgorithm or the like) of the vehicle side and door handles in thecaptured image for verifying the camera mounting is within the desiredor appropriate tolerance limit. The algorithm may further perform a finestructure fitting (such as via a correlation algorithm or contourfitting algorithm or the like) for calculating shift in yaw, pitch androll. As shown in FIGS. 3A-C, the actual or detected vehicle edges maybe misaligned or separated from the expected vehicle edges, such thatthe image processing may be adjusted to shift the captured image dataaccordingly to accommodate such misalignment of the camera. Based on theresults of the image processing techniques, data or information of theyaw, pitch and roll may be used to set the polygon co-ordinates and Hdepression pixel calibration parameters, so that the expected vehicleedges are substantially aligned with the actual or detected vehicleedges.

After the image data or image processing is adjusted to account for anymisalignment of the camera at the vehicle, the camera may capture imagesof the scene occurring exteriorly of the vehicle and at that side of thevehicle, and the control may process the images to detect objects orlane markers or the like at the side of the vehicle and/or rearward ofthe vehicle, and may utilize aspects described in U.S. patentapplication Ser. No. 10/427,051, filed Apr. 30, 2003 by Pawlicki et al.for OBJECT DETECTION SYSTEM FOR VEHICLE, now U.S. Pat. No. 7,038,577,which is hereby incorporated herein by reference.

Adjustment of Zone when Vehicle Turning:

Optionally, the control may perform a curve processing or lane dividercurve fitting function to select or adjust the reduced image set or zoneof interest based on a steering angle of the vehicle (the angle at whichthe vehicle is steered to either side relative to the longitudinal axisof the vehicle), such as when the front wheels of the subject vehicleare turned. The curve processing function may adjust the zone ofinterest based on the degree of turning of the steering wheel (or othercharacteristic indicative of the steering angle of the vehicle) so thatareas or regions outside of a revised curve may not be processed orconsidered as much as the areas or regions within the revised curve.Based on the history of host vehicle information (such as vehicle speedand wheel angle), the control may modify the slope of the adjacent lanedivider (at the left side of user specified area of interest) atdifferent positions. As shown in FIG. 4, when the wheels are turned atan angle θ, the control may determine a new curved line 40 thatrepresents the edge of the zone or area of interest. This modificationwill convert straight line 1-5 in FIG. 4 to the curve 40. Detectedtargets or objects outside this, curve (i.e., to the left of the curvein FIG. 4) will not be considered for the mapping or object detection.As shown in FIG. 5, the wheel angle may be determined by the rotation orpivoting or turning of the front wheels of the vehicle about theirgenerally vertical axis (which may be detected by a rotational measuringdevice or the like), and the curve may be adjusted as a function of thevehicle speed (such as determined via a wheel speed sensor or the like)and the wheel angle θ.

The following vehicle information history table (VIHT) with the historyof multiple (N) frames or captured images may be maintained for fittingof a curve. The table may be updated when the vehicle information isavailable for each frame.

Host Vehicle Information (VI_(n)) Frame Index/ Wheel Cumulative Point onTime Stamp Speed Angle Wheel Angle Point on Curvature (cm) Curvature(pixels) T_(n) V_(n) θ_(n) θ_(Cn) X_(n) Y_(n) X_(Pn) Y_(Pn) T₀ V₀ θ₀θ_(C0) X₀ Y₀ X_(P0) Y_(P0) T₁ V₁ θ₁ θ_(C1) X₁ Y₁ X_(P1) Y_(P1) T₂ V₂ θ₂θ_(C2) X₂ Y₂ X_(P2) Y_(P2) . . . . . . . . . . . . . . . . . . . . . . .. T_(N-1) V_(N-1) θ_(N-1) θ_(C(N-1)) X_(N-1) Y_(N-1) X_(P(N-1))Y_(P(N-1)) T_(N) V_(N) θ_(N) θ_(CN) = θ_(REF) X_(N) = X_(REF) Y_(N) =Y_(REF) X_(PN) Y_(PN)

During operation, the control may perform the following computations:

-   -   1. Compute Reference Angle (θ_(REF)) using polygon vertices (1 &        5).    -   2. Compute Reference Point (X_(REF), Y_(REF)) using Reference        Angle (θ_(REF)) and Mirror Wheel Separation Distance (D).    -   3. For each frame update (add in the circular buffer) following        VIHT entries:        -   a. Frame Index or Time Stamp (T_(n));        -   b. Host Vehicle Speed (V_(n)); and        -   c. Host Vehicle Wheel Angle (θ_(n)) (note that this angle            may be considered without doing any perspective correction,            but may require appropriate correction to be added based on            height and angle of inclination of the camera).    -   4. Compute Cumulative Wheel Angle (θ_(Cn)):        -   θ_(CN)=θ_(REF);        -   θ_(C(N−1))=θ_(N−1+)θ_(CN);        -   θ_(C(N−2))=θ_(N−2+)θ_(C(N−1));        -   θ_(C(N−3))=θ_(N−3+)θ_(C(N−2));        -   .        -   .        -   .        -   θ_(C0=)θ₀₊θ_(C1).    -   5. Compute curve points (X_(n), Y_(n)) (such as in cm):    -    The n=N curve point is a reference point and for all other        points the following equations may be used to compute the curve        points:        Y _(N−1) =F1(T _(N−1) ,V _(N−1) ,Y _(N)); and        X _(N−1) =F2(θ_(C(N−1),) Y _(N−1) ,X _(N) ,Y _(N))    -    Preferably, the functions F1 and F2 are relatively simple        trigonometric functions.    -   6. Replace the curve point (X₀, Y₀) with the intersection point        of the curve and the horizon, and preferably do not allow the        curve to cross the horizon.    -   7. For display purposes, compute the curve points (X_(Pn),        Y_(Pn)) in pixels using the existing cm—pixel relations        (CMDistances and PixelSomethingThreshold)

In a preferred embodiment, the steps 1 and 2 above may be a one timecomputation in the initialization part of the algorithm, while the steps3-6 are preferably executed during the run-time of the system, and thestep 7 preferably is executed in the debug mode for the testing.

Vertical Edge Detection:

Optionally, the object detection system may be operable to detectvertical edges of objects in the field of view of the Camera. Such anapproach may be useful in detecting target vehicles when the front ofthe target vehicle is not visible, such as when the target vehicle isalongside the subject vehicle.

The vertical edge detection algorithm may be performed first at a lowlevel Processing. During such low level processing, the vertical edgedetection may be applied to an input image, and a noise filteringalgorithm may be applied to the edge image. The lateral X histogram maybe calculated and analyzed; and any non-significant edge counts may beremoved from the histogram. The histogram may be normalized and analyzedto identify probable targets, a different ID may be given for a verticaledge detected target for use during high level processing.

During the high level processing, a map of target information forvertical targets may be generated, such as in a similar manner as forhorizontal edge detected targets (such as described in U.S. patentapplication Ser. No. 10/427,051, filed Apr. 30, 2003 by Pawlicki et al.for OBJECT DETECTION SYSTEM FOR VEHICLE, now U.S. Pat. No. 7,038,577,which is hereby incorporated herein by reference, and such as describedbelow). The targets may be filtered out based on various criteria (suchas relative speed, number of frames present and/or the like), and awarning may be raised or generated if the object is detected at the sideof the'vehicle.

Such vertical edge detection functions may be desirable, since a targetvehicle's trunk may generate a significant vertical edge. Also, thevertical edges may substantially always be present in both the daytimeand nighttime hot zones. Furthermore, tree shadows; lane markings andother structures may be filtered out using such vertical edge detection.

Qualification During Daytime:

Side Object Detection works based on the edges detected. Horizontaledges are used to detect and track vehicle. The detected edges arequalified based on a robust high level vision algorithm, such as thealgorithms described in U.S. patent application Ser. No. 10/427,051,filed Apr. 30, 2003 by Pawlicki et al. for OBJECT DETECTION SYSTEM FORVEHICLE, now U.S. Pat. No. 7,038,577, which is hereby incorporatedherein by reference. Vertical edges are being used to detect vehiclesclose to the camera/passing vehicles, as discussed above.

However, the vehicle identification may be based on the shadow createdby the vehicle (for day time operation). A detected shadow could becreated by a target vehicle entering into the blind spot or staticobjects like guard rails or structures on the road side or by the selfshadow (of the subject vehicle) or of vehicles passing more than onelane away. It is difficult to identify whether or not the shadow is by atarget vehicle entering into the blind spot. Thus, a positiveidentification or qualification of the edges can help in reducing falsealarms.

When a shadow is detected, it is either a shadow created by a vehicleentering into the blind spot, or a shadow created by something else andnot the target vehicle (a vehicle entering the blind spot). Referring toFIGS. 6-9, different shadows are shown for different scenarios thesystem may encounter, such as, for example, the shadow cast by a truckthat is one or more lanes over from the target lane (FIG. 6), shadowscast by trees alongside the road (FIG. 7), the shadow cast by thesubject vehicle (FIG. 8), and/or dark structures (FIG. 9).

In the case where the shadow is created by something other than thetarget vehicle, the following characteristics may be assumed:

-   -   1. Below the edge (for horizontal edges) the road may have full        illumination by daylight, and above the horizontal edge there        will be road where daylight is partially occluded by some        objects (so lesser illumination); or    -   2. Below the edge the road may be darker because of partial        occlusion by some object causing the shadow, and above the edge        the road may have full daylight illumination;    -   3. The above two scenarios are similar for the areas to the left        and right of a vertical shadow.

Therefore, the following characteristics can also be assumed:

-   -   1. Above and below the edges there is road;    -   2. To the left and right of a vertical edge there is road;    -   3. One side of the edge is not road but is a vehicle.

The problem is that it has heretofore been difficult to distinguishbetween the shadow and the vehicle. The proposed methodology is intendedto increase the confidence in decision. For example, the situations inFIGS. 6 and 7 may cause the system to indicate that it is a falsepositive (host or self shadow removal (discussed below) will also beresolved), while the situation in FIG. 8 may cause the system toindicate that the edge is due to a vehicle. The situation in FIG. 9 mayresult in the system indicating that it could not decide so the existingalgorithm should continue to process the images.

In order to qualify a detected edge, the system of the present inventionmay perform the following processing steps:

-   -   1. Histogram Analysis:        -   display the edge pixels within the hot zone;        -   determine the start and the endpoint of an edge;        -   create processing windows on either side of the edge; and        -   perform wide line integration.

For Example, and as shown in FIGS. 10 and 11, a plurality of processingwindows may be applied at either side of a detected edge. A plot as aresult of the wide line integration is expected to be as shown in FIG.12. The variations in the plot are expected to provide insight inqualifying an edge.

-   -   2. Extracting unique features across the edge (mean and range):        -   display the edge pixels within the hot zone;        -   determine the start and the endpoint of an edge;        -   estimate unique features to qualify an edge such as mean and            range; and        -   analyze variations in mean and range on either side of the            edge.

Comparison of the mean and range of the processing windows across adetected edge is expected to give insight in qualifying an edge.

-   -   3. Gradient analysis across the detected horizontal edge:        -   display the edge pixels within the hot zone;        -   determine the start and the endpoint of an edge;        -   gradient calculations are done on the processing windows            using local window operators, such as Sobel operators of the            mask shown in FIG. 13; and        -   The gradient magnitude gives the amount of the difference            between pixels in the neighborhood (the strength of the            edge). The gradient orientation gives the direction of the            greatest change, which presumably is the direction across            the edge (the edge normal). Comparison of the gradient            across the edge is expected to provide insight in qualifying            an edge.            Host Shadow Removal:

In side object detection, the host shadow of the vehicle may be detectedas a target vehicle if the host shadow is extended in the hot zone (orzone or area of interest alongside the subject or host vehicle). Often,the host shadow may fall on the adjacent lane in the morning or eveningtime. The host shadow consists of a straight horizontal edge and an edgeline with some slope, such as shown in FIG. 14.

The steps involved in processing the image to remove or ignore the hostshadow include:

-   -   obtain the target list at the output of processframe( );    -   for each target, get the row value (y_Pixel);    -   trace for the horizontal edge line around this row value;    -   check whether this line is continuous, starting from the subject        vehicle body (approximately) and up to and after the lower        border of the hot zone;    -   check whether this horizontal edge is extended in the hot zone        and has a significant pixel count in the hot zone (check against        the pixel something threshold for that particular line);    -   start tracing for the sloped edge line at the end of this        horizontal edge;    -   if the sloped line is present for some columns it means that        there is a host shadow; and    -   if there is a host shadow, remove the corresponding target from        the target list.

Note that this process may be applied before calculating the targetlist, so that the host shadow edge pixel count can be subtracted fromthe line counts. In such an application, all the lines may be scanneduntil the detection of the host shadow. Vertical edge calculations maynot be needed for this process, since, often, if the horizontal edgeline of the host shadow is present in the hot zone then the host shadowis getting detected.

Bicycle Detection:

The side object detection system may be operable to detect otherobjects, such as a bicycle in the zone of interest. For a bicycle, thereare small edges compared to a target vehicle, since the bicycle tire issmall. In order to detect and track such small edges, we need to tunesome of the parameters. For example, some or all of the following listedparameters may be changed to enhance the ability of the system to detecta bicycle:

-   -   SOMETHING_SIZE_CM: some size of the object in cms for reference        (Calibration.h);    -   gCalibration.SMOOTHING_ALG_THRESHOLD: threshold applied on the        peak normal force of the vehicle to see if the detected vehicle        was significant (FindEdgePeaks_A( ));    -   gCalibration.XFILTER_FACTOR: with the pixelsomething threshold        of a line, it decides the minimum number of horizontal pixels        required for a valid object/target (XFilterNew( ));    -   gCalibration.HOT_ZONE_COUNT_THRESHOLD_DIVISOR: divisor factor of        pixel something threshold of a line at the time of detection of        valid objects (ComputeLineCountsR( ));    -   gCalibration.X_MUST_WARN: the maximum distance for a target to        create a warning (when a target is located inside this position        (Target X<X Must Warn), a warning for that target may be        displayed);    -   gCalibration.VD_HYSTERESIS_ON: threshold (normal force) at which        the algorithm determines a starting point of a target        (FindEdgePeaks_A( ));    -   gCalibration.VD_HYSTERESIS_OFF: threshold at which the algorithm        determines the falling off point of a target (FindEdgePeaks_A(        ));    -   gCalibration.LINEERROR: this is the difference between the        projected distance and actual distance of a particular target        (i.e. line mapping error).

With the parameter tuning, the system may detect many false edges aswell. In order to reduce such false edge detections, the vertical edgedetection may be used as an additional feature.

Vertical Edge Detection:

-   -   detect the vertical edges for the frame in the area of interest        region;    -   the vertical edge image is scanned for the connected pixels        along the columns;    -   the maximum connected pixels count is compared against the        threshold;    -   based on the comparison result, the decision is made as to        whether the target is present or absent.

The Vertical Edge Image May be Scanned in the Following Regions:

-   -   Lower limit: the lower limit of the area of interest;    -   Upper limit: the upper boundary of the nighttime hot zone        (FarCenterIndices_N).        This is to reduce or substantially avoid a false vertical edge        detection of objects outside the adjacent lane. The vertical        edges may correspond to the wheels. When the target vehicle is        far away, the vertical edge count will be small, and when the        target vehicle is closer, the vertical edge count will be        greater. A threshold count may be selected to provide the        desired accuracy of the system.

The bicycle detection algorithm may be applied during the daytimebecause the bicycle headlight can be detected with the existingparameters (to be verified), and because little or no vertical edges maybe detected during the night time (the detected vertical edges aremainly because of the wheels). Because the bicycle speed is typicallylow compared to the vehicle speed, the bicycle detection algorithm maybe triggered only when the host vehicle speed goes below some thresholdspeed (such as at or below approximately 20 kph or thereabouts, forexample). A flow chart of the bicycle detection process is shown: inFIG. 15.

Without the vertical edge detection, some situations may result in falsedetections. For example, speed breakers beside the road (the system maynot consider these as stationary objects because they continuously haveedges one after the other which may map with the previous ones, so thatsome frames in this region are detected as targets), bisectors (theshadow of the bisector may create edges at the upper side of the image,in this region small pixel counts results in edge detection and mayresult in a detection of a target), roadside dark areas with small whitepatches. With vertical edge detection as an additional feature, theabove false detections may be improved.

Also, it is envisioned that a bicycle rider may not always move straightlike a vehicle in the lane. If the front wheel swings, then theprojected target may not match with the current detected position. Inorder to account for this, the line error parameter may be adjusted tosome extent. Also, it may be difficult to detect a bicycle if there is ashadow on the road and the bicycle is on the shadowed part of the road.

Target Mapping Tolerance:

Optionally, the object detection system and control may provide a nearfield detection or target mapping tolerance—line error function. Such adetection may utilize use inputs or calibration parameters. For example,a line error image may provide target-mapping tolerances in the imagespace due to car vibrations (such as about 3 to 6 pixels), or errors inthe image processing (e.g. about 1 pixel for an edge filter), or otherinputs. Also, a minimum line error (physical) input may provide targetmapping tolerances in the physical space due to small variations in thetarget vehicle speed (this calibration parameter may be in terms ofcms). Likewise, a target speed tolerance factor (such as between 0-100)may provide target mapping tolerances in the physical space, as expectedto change with the speed of a target. This factor may determine the sizeof a tolerance band.

During operation of the object detection system, the control may computethe tolerance (the line error pixels) to be used for the target mapping,which may change with the distance from the camera (i.e., the tolerancemay be different for the different lines in the image).

The following provides computations/functions that the control mayperform to determine the tolerances and the like.

For example, the computation for the N^(th) line:LineErrorPixels=MAX (LineErrorImage, LineErrorPhysicalInPixels_(—) N).LineErrorPhysicalInPixels_(—) N=CMtoPIXEL (LineErrorPhysical, N).

CMtoPIXEL (LineErrorPhysical, N) is a function that will convert lineerror in cm to pixels for a specified line.LineErrorPhysical=MAX (MinLineErrorPhysical, LineErrorPhysicalWindow).LineErrorPhysicalWindow=(TargetSpeedToleranceFactor*ExpectedDistanceCoveredByTarget)/100.ExpectedDistanceCoveredByTarget=TargetRelativeSpeed*FrameRate.Day/Night Switch Algorithm:

Optionally, the side object detection system may switch between adaytime sensitivity and a nighttime sensitivity. For example, thealgorithm may include the following steps:

-   -   1. Compute image histogram (H);    -   2. compute accumulated image histogram (Ha) using last N (such        as, for example, 30) frames;    -   3. divide Ha into the following four regions:        -   (1) dark (0<Gray Level<=Td);        -   (2) night (Td<Gray Level<=Tdn);        -   (3) day (Tdn<Gray Level<Tb); and        -   (4) bright (Tb<=Gray Level<=255),        -   using following three thresholds:        -   (1) Td (0): dark threshold;        -   (2) Tdn (80): day-night threshold (which may be selected in            such a way that it separates day (with/without shadow) from            the night (with/without headlights); this may be a fixed            threshold computed using arithmetic mean or a geometric mean            and auto-threshold); and        -   (3) Tb (255): bright threshold that is used to separate            headlight and overexposed (during day) pixels;    -   4. count number of pixels into above four regions:        -   (1) dark region count (Cd);        -   (2) night region count (Cn);        -   (3) day region count (Cy); and        -   (4) bright region count (Cb),        -   and compute:        -   (1) difference in Cy and Cn in % of total pixels (Ddn)            [where Ddn=(ABS(Cy−Cn)*100)/ImagePixelCount]; and        -   (2) extreme peak count (Cd+Cb) in % of total pixels (P)            [where P=((Cd+Cb)*100)/ImagePixelCount]; and    -   5. apply the following rules to make a decision:

Rule No. Condition(s) Situation Decision 1 Cn > Cy Clear Night NightDdn >= T1 (sufficient pixels in night region) 2 Cy > Cn Clear Day DayDdn >= T1 (sufficient pixels in day region) 3 Cn > Cy Night + HeadlightsNight Ddn < T1 P >= T2 (Extreme peak found) 4 Cn > Cy Night + StreetLight, No Ddn < T1 Day + Clouds, Decision P < T2 (No extreme Day +Shadow (Previous peak found) State) 5 Cn < Cy Day + Overexposure, No Ddn< T1 Day + Snow, Decision P >= T2 (Extreme Night + Blooming (Previouspeak found) Headlights State) 6 Cn < Cy Day + Shadow Day Ddn < T1 P < T2(No extreme peak found)

For example, T1=70 percent and T2=2 percent. For rule 4 and 5,additional features may be desired, since the available features may notin all cases be sufficient to differentiate between day and night. If nodetermination or differentiation is made, the previous state may beretained. The processing time for each frame may be around 1 ins orthereabouts, such as about 0.7 ms.

Headlight Detection:

Optionally, a headlight detection module may be used to improve thenighttime target detection results. Such a module may be integrated withthe side object detection algorithm. The headlight detection module oralgorithm may use optimized blob analysis code in area of interest, andmay identify clusters in an image during nighttime detection mode. Theheadlight detection module or algorithm may separate out headlights, andsaturated and unqualified clusters of lights, and may be able todistinguish between headlights and reflections caused by headlights. Theheadlight detection module or algorithm may minimize false detectionscaused because of reflections on the road, or non-headlight lightsources. The headlight detection module may detect the position of theheadlight, and thus may provide enhanced positional accuracy whiletarget detection. The headlight detection module may also be useful indusk and dawn condition.

It is envisioned that, by analysis of the saturated clusters, the cameragain and exposure can be controlled in close loop, and thus theday/night switch detection can be improved. It is further envisionedthat, for more accuracy, the system may detect both headlights to assistin making the decision of target detection (such as for detecting carsand/or trucks). Also, most or substantially all of the saturated and notqualified clusters may be examined for possible merging of twoheadlights, such as when the vehicle is far away from the camera on thesubject or host vehicle.

Referring now to FIGS. 16-20, the process of identifying the headlightsof a target vehicle is shown. As shown in FIG. 16, the headlights andtheir reflections are identified, and, as shown in FIGS. 17 and 18, theparticular location or position of the headlight/headlights isidentified as a target position. The non-headlight sources areidentified separately (FIG. 19), and the saturated clusters areidentified (FIG. 20), such as may be useful in close loop control of theside object detection system.

The table below indicates the effect on the timing of thedetection/identification of side objects, as shown with and without theheadlight detection function:

With Headlight Without Headlight Detection Detection Modules(mili-second) (mili-second) Process Line 17.5 17.5 Generate Edge image3.4 3.4 Process Frame 17.5 17.45 Map Targets 1 1 Headlight Detection12.9 — Total 52.3 39.35 Frame Rate 15 FPS 15 FPS

Optionally, the side object detection system and/or the imaging sensoror camera may be associated with other imaging systems or controls, suchas imaging systems having an image sensor (such as a video camera, suchas a CMOS imaging array sensor, a CCD sensor or the like, such as thetypes of imaging sensors or cameras disclosed in commonly assigned, U.S.Pat. Nos. 5,550,677; 6,097,023 and 5,796,094, and/or PCT Application No.PCT/US2003/036177, filed Nov. 14, 2003 by Donnelly Corp. for IMAGINGSYSTEM FOR VEHICLE, which are hereby incorporated herein by reference),such as a forward facing video image sensor or system, which may includeor may be associated with an intelligent rain sensor (such as the typesdisclosed in commonly assigned U.S. Pat. Nos. 6,320,176; 6,353,392 and6,313,454, which are hereby incorporated herein by reference), an imageor vision system (including an imaging sensor, such as a video camera,such as a CMOS imaging array sensor, a CCD sensor or the like, such asthe types disclosed in commonly assigned, U.S. Pat. Nos. 5,550,677;6,097,023 and 5,796,094, and U.S. patent application Ser. No.10/422,378, filed Apr. 24, 2003 by Schofield for IMAGING SYSTEM FORVEHICLE, now U.S. Pat. No. 6,946,978, which are hereby incorporatedherein by reference), such as an imaging or object detection system orback up aid of the types described in U.S. Pat. Nos. 6,757,109;6,717,610; 6,590,719; 6,201,642; 5,929,786; and/or 5,786,772, and/orU.S. patent application Ser. No. 10/427,051, filed Apr. 30, 2003 byPawlicki et al. for OBJECT DETECTION SYSTEM FOR VEHICLE, now U.S. Pat.No. 7,038,577; and/or Ser. No. 11/239,980, filed Sep. 30, 2005 byCamilleri et al. for VISION SYSTEM FOR VEHICLE, now U.S. Pat. No.7,881,496, and/or U.S. provisional applications, Ser. No. 60/628,709,filed Nov. 17, 2004 by Camilleri et al. for IMAGING AND DISPLAY SYSTEMFOR VEHICLE; Ser. No. 60/614,644, filed Sep. 30, 2004; and/or Ser. No.60/618,686, filed Oct. 14, 2004 by Laubinger for VEHICLE IMAGING SYSTEM,which are hereby incorporated herein by reference, or an intelligentheadlamp controller (such as the types described in U.S. Pat. Nos.5,796,094; 5,715,093; and/or 6,824,281, and/or in U.S. pat. applicationSer. No. 10/958,087, filed Oct. 4, 2004 by Schofield et al. for VEHICLEACCESSORY MODULE, now U.S. Pat. No. 7,188,963; and/or Ser. No.11/105,757, filed Apr. 14, 2005, now U.S. Pat. No. 7,526,103, and/orU.S. provisional applications, Ser. No. 60/607,963, filed Sep. 8, 2004by Schofield for IMAGING SYSTEM FOR VEHICLE; and Ser. No. 60/562,480,filed Apr. 15, 2004 by Schofield for IMAGING SYSTEM FOR VEHICLE, whichare hereby incorporated herein by reference), or an intelligent lanedeparture warning system (such as the types described in U.S. patentapplication Ser. No. 10/209,173, filed Jul. 31, 2001 by Schofield forAUTOMOTIVE LANE CHANGE AID, now U.S. Pat. No. 6,882,287; and/or Ser. No.10/427,051, filed Apr. 30, 2003 by Pawlicki et al. for OBJECT DETECTIONSYSTEM FOR VEHICLE, now U.S. Pat. No. 7,038,577, which are herebyincorporated herein by reference), and/or the like.

Optionally, the side object detection system of the present inventionmay include one or more displays, such as a text display, an icondisplay, a display on demand (DOD) type display (such as may beimplemented with a transflective reflective element, such as describedin U.S. Pat. Nos. 5,668,663; 5,724,187; and 6,690,268, the entiredisclosures of which are hereby incorporated by reference herein), suchas a video or touch screen interface display, or a video display screen,such as the types described in PCT Application No. PCT/US03/40611, filedDec. 19, 2003 by Donnelly Corp. et al. for ACCESSORY SYSTEM FOR VEHICLE,and/or U.S. pat. application Ser. No. 10/538,724, filed Jun. 13, 2005and published Mar. 9, 2006 as U.S. Publication No. US-2006-0050018; andSer. No. Ser. No. 11/284,543, filed Nov. 22, 2005 by DeWind et al. forINTERIOR MIRROR ASSEMBLY WITH DISPLAY, now U.S. Pat. No. 7,370,983;and/or U.S. provisional applications, Ser. No. 60/630,061, filed Nov.22, 2004 by Lynam et al. for MIRROR ASSEMBLY WITH VIDEO DISPLAY; andSer. No. 60/667,048, filed Mar. 31, 2005, which are hereby incorporatedherein by reference, or the like.

Therefore, the present invention provides a side object detection systemthat is operable to process captured image data of a scene occurringexteriorly and along one or both sides of the vehicle to determine if atarget vehicle or object of interest is located at or in the laneadjacent to the subject or host vehicle. The side object detectionsystem of the present invention may process zones or areas of interestin the captured images and may adjust processing to accommodate anymisalignment of the camera that may occur during installation of thecamera at the side of the vehicle. The side object detection system mayalso adjust the processing to adjust the areas of interest, such as inresponse to a turning of the wheels of the vehicle so that the zone orarea is adapted for the turning of the subject vehicle. The side objectdetection system may detect horizontal edges and vertical edges ofobjects in the exterior scene and may identify shadows and discern theshadows in the adjacent lane (which may be shadows cast by objectsoutside of the adjacent lane) from objects or target vehicles that maybe present in the adjacent lane. The side object detection system of thepresent invention may also discern or distinguish between daytime andnighttime conditions and may adjust the image processing accordingly.The side object detection system may also function to detect headlightsof a target vehicle in the adjacent lane and to discern or distinguishthe headlights of the target vehicle from other light sources, such asreflections or other non-qualified light sources. The side objectdetection system of the present invention thus provides enhanced imageprocessing and may utilize aspects of the side object detection systemdescribed in U.S. patent application Ser. No. 10/209,173, filed Jul. 31,2001 by Schofield for AUTOMOTIVE LANE CHANGE AID, now U.S. Pat. No.6,882,287; and/or Ser. No. 10/427,051, filed Apr. 30, 2003 by Pawlickiet al. for OBJECT DETECTION SYSTEM FOR VEHICLE, now U.S. Pat. No.7,038,577, which are hereby incorporated herein by reference.

Changes and modifications in the specifically described embodiments canbe carried out without departing from the principles of the presentinvention, which is intended to be limited only by the scope of theappended claims as interpreted according to the principles of patentlaw.

1. An imaging system for a vehicle, said imaging system comprising: animaging array sensor comprising a plurality of photo-sensing pixels,wherein said imaging array sensor is disposed at an exterior rearviewmirror assembly at a side of a vehicle equipped with said imagingsystem; wherein, when said imaging array sensor is disposed at theexterior rearview mirror assembly, said imaging array sensor has a fieldof view exterior of the equipped vehicle, and wherein said imaging arraysensor is operable to capture an image exterior of the equipped vehicle;a control for processing said captured image; wherein said control isoperable to determine that said imaging array sensor is misaligned whensaid imaging array sensor is disposed at the exterior rearview mirrorassembly at the side of the equipped vehicle; and wherein said control,responsive to a determination of misalignment of said imaging arraysensor, is operable to at least partially compensate for the determinedmisalignment of said imaging array sensor.
 2. The imaging system ofclaim 1, wherein said imaging array sensor is disposed at leastpartially within the exterior rearview mirror assembly at the side ofthe equipped vehicle.
 3. The imaging system of claim 2, wherein saidfield of view of said imaging array sensor encompasses at least one of(a) a rearward field of view exterior of the equipped vehicle and (b) asideward field of view exterior of the equipped vehicle.
 4. The imagingsystem of claim 3, wherein said field of view of said imaging arraysensor encompasses a forward field of view exterior of the equippedvehicle.
 5. The imaging system of claim 1, wherein said control isoperable to determine that said imaging array sensor is aligned within adesired tolerance when said imaging array sensor is disposed at theexterior rearview mirror assembly at the side of the equipped vehicle.6. The imaging system of claim 1, wherein said control, responsive to adetermination of misalignment of said imaging array sensor, is operableto adjust processing of said captured image to at least partiallycompensate for the determined misalignment of said imaging array sensor.7. The imaging system of claim 1, wherein said captured image comprisesdata and wherein said control, responsive to a determination ofmisalignment of said imaging array sensor, is operable to adjust saiddata to at least partially compensate for the determined misalignment ofsaid imaging array sensor.
 8. The imaging system of claim 1, whereinsaid imaging array sensor has a field of view that encompasses a portionof the equipped vehicle.
 9. The imaging system of claim 8, wherein saidimaging array sensor has a field of view that encompasses a portion ofthe side of the equipped vehicle at which said imaging array sensor isdisposed.
 10. The imaging system of claim 9, wherein processingundertaken by said control at least partially accounts for misalignmentof said imaging array sensor at the side of the equipped vehicle atleast in part responsive to image data captured of the portion of theside of the equipped vehicle encompassed by said field of view of saidimaging array sensor.
 11. The imaging system of claim 10, wherein saidfield of view encompasses a structure at the side of the vehicle atwhich said imaging array sensor is disposed.
 12. The imaging system ofclaim 1, wherein said captured image comprises data and wherein saidcontrol processes said data to determine a location of a referencestructure at the side of the equipped vehicle at which said imagingarray sensor is disposed, and wherein said control, responsive toprocessing of said data, is operable to verify that said imaging arraysensor is aligned at the side of the equipped vehicle within a desiredtolerance.
 13. The imaging system of claim 1, wherein said control,responsive to a determination of misalignment of said imaging arraysensor, is operable to determine a degree of misalignment of saidimaging array sensor.
 14. The imaging system of claim 13, wherein saidcontrol, responsive to a determination of the degree of misalignment ofsaid imaging array sensor, is operable to at least partially compensatefor the determined degree of misalignment of said imaging array sensor.15. The imaging system of claim 14, wherein said control processes saidcaptured image to detect a reference structure at the side of theequipped vehicle, and wherein said control is operable to adjust saidprocessing to position the reference structure at an appropriatelocation in the captured image to at least partially compensate for thedetermined degree of misalignment of said imaging array sensor.
 16. Theimaging system of claim 1, wherein said control algorithmicallyprocesses data of said captured image to a reduced data set of saiddata, said control processing said reduced data set to extractinformation from said reduced data set.
 17. The imaging system of claim16, wherein said reduced data set is representative of a target zone ofsaid captured image.
 18. The imaging system of claim 1, wherein saidcontrol processes said captured image to detect an object exterior theequipped vehicle.
 19. The imaging system of claim 1, wherein saidcontrol is operable to distinguish between an object in the field ofview of said imaging array sensor and a shadow of an object.
 20. Theimaging system of claim 1, wherein said control is operable to switchbetween daytime and nighttime algorithms in response to an ambient lightlevel at the equipped vehicle.
 21. The imaging system of claim 1,wherein said control is operable to alert the driver of the equippedvehicle that an object is detected exterior to the equipped vehicle. 22.The imaging system of claim 1, wherein said control is operable to alertthe driver of the equipped vehicle that an object is detected at theside of the equipped vehicle in response to at least one of (a) thedriver of the equipped vehicle actuating a turn signal toward the sideof the equipped vehicle at which the object is detected, and (b) thedriver of the equipped vehicle steering the equipped vehicle toward theside of the equipped vehicle at which the object is detected.
 23. Theimaging system of claim 1, wherein said control applies an edgedetection algorithm to process data of said captured image.
 24. Theimaging system of claim 23, wherein an algorithmically executedfiltering mechanism at least substantially ignores detected edges thatare not indicative of a significant object in order to at least one of(a) reduce a processing requirement and (b) reduce false signals. 25.The imaging system of claim 1, wherein said imaging array sensor has afield of view at least partially sideward of the equipped vehicle, saidimaging system comprising a side object detection system for detectingan object at a side of the equipped vehicle.
 26. The imaging system ofclaim 1, wherein said imaging array sensor comprises a CMOS imagingarray sensor.
 27. An imaging system for a vehicle, said imaging systemcomprising: an imaging array sensor comprising a plurality ofphoto-sensing pixels, wherein said imaging array sensor is disposed atan exterior rearview mirror assembly at a side of a vehicle equippedwith said imaging system; wherein, when said imaging array sensor isdisposed at the exterior rearview mirror assembly, said imaging arraysensor has a field of view exterior of the equipped vehicle and whereinsaid field of view encompasses a portion of the side of the equippedvehicle at which said imaging array sensor is disposed, and wherein saidimaging array sensor is operable to capture an image exterior of theequipped vehicle that includes the portion of the side of the equippedvehicle encompassed by said field of view of said imaging array sensor;a control for processing said captured image; wherein said control, atleast in part responsive to processing of said captured image, isoperable to determine that said imaging array sensor is misaligned whensaid imaging array sensor is disposed at the exterior rearview mirrorassembly at the side of the equipped vehicle; and wherein said control,responsive to a determination of misalignment of said imaging arraysensor, is operable to at least partially compensate for the determinedmisalignment of said imaging array sensor.
 28. The imaging system ofclaim 27, wherein said field of view encompasses a structure at the sideof the vehicle at which said imaging array sensor is disposed.
 29. Theimaging system of claim 27, wherein said captured image comprises dataand wherein said control, responsive to a determination of misalignmentof said imaging array sensor, is operable to adjust said data to atleast partially compensate for the determined misalignment of saidimaging array sensor.
 30. The imaging system of claim 29, wherein saidcontrol, responsive to a determination of misalignment of said imagingarray sensor, is operable to adjust processing of said data.
 31. Theimaging system of claim 29, wherein processing undertaken by saidcontrol at least partially accounts for misalignment of said imagingarray sensor at the side of the equipped vehicle at least in partresponsive to processing of data captured of the portion of the side ofthe equipped vehicle encompassed by said field of view of said imagingarray sensor.
 32. The imaging system of claim 27, wherein said imagingarray sensor is disposed at least partially within the exterior rearviewminor assembly at the side of the equipped vehicle.
 33. The imagingsystem of claim 32, wherein said field of view of said imaging arraysensor encompasses at least one of (a) a rearward field of view exteriorof the equipped vehicle, (b) a sideward field of view of the equippedvehicle and (c) a forward field of view exterior of the equippedvehicle.
 34. The imaging system of claim 27, wherein said control isoperable to determine that said imaging array sensor is aligned within adesired tolerance when said imaging array sensor is disposed at theexterior rearview mirror assembly at the side of the equipped vehicle.35. The imaging system of claim 27, wherein said control processes saidcaptured image to determine a location of a reference structure at theside of the equipped vehicle at which said imaging array sensor isdisposed, and wherein said control, responsive to processing of saidcaptured image, is operable to verify that said imaging array sensor isaligned at the side of the equipped vehicle within a desired tolerance.36. An imaging system for a vehicle, said imaging system comprising: animaging array sensor comprising a plurality of photo-sensing pixels,wherein said imaging array sensor is disposed at least partially withinan exterior rearview mirror assembly at a side of a vehicle equippedwith said imaging system; wherein, when said imaging array sensor isdisposed at least partially within the exterior rearview mirrorassembly, said imaging array sensor has a field of view exterior of theequipped vehicle, and wherein said imaging array sensor is operable tocapture an image exterior of the equipped vehicle; a control forprocessing said captured image; wherein said control is operable todetermine that said imaging array sensor is misaligned when said imagingarray sensor is disposed at least partially within the exterior rearviewmirror assembly at the side of the equipped vehicle; wherein saidcontrol, responsive to a determination of misalignment of said imagingarray sensor, is operable to at least partially compensate for thedetermined misalignment of said imaging array sensor; and wherein saidcaptured image comprises data and wherein said control processes saiddata to determine a structure at the side of the equipped vehicle atwhich said imaging array sensor is disposed, and wherein said control,responsive to processing of said data, is operable to verify that saidimaging array sensor is aligned at the side of the equipped vehiclewithin a desired tolerance.
 37. The imaging system of claim 36, whereinsaid field of view of said imaging array sensor encompasses at least oneof (a) a rearward field of view exterior of the equipped vehicle, (b) asideward field of view of the equipped vehicle and (c) a forward fieldof view exterior of the equipped vehicle.
 38. The imaging system ofclaim 36, wherein said control, responsive to a determination ofmisalignment of said imaging array sensor, is operable to adjust saiddata to at least partially compensate for the determined misalignment ofsaid imaging array sensor.
 39. The imaging system of claim 38, whereinsaid control, responsive to a determination of misalignment of saidimaging array sensor, is operable to adjust processing of said data. 40.The imaging system of claim 36, wherein said control is operable todetermine that said imaging array sensor is aligned within a desiredtolerance when said imaging array sensor is disposed at least partiallywithin the exterior rearview mirror assembly at the side of the equippedvehicle.
 41. An imaging system for a vehicle, said imaging systemcomprising: an imaging array sensor comprising a plurality ofphoto-sensing pixels, wherein said imaging array sensor is disposed atleast partially within an exterior rearview mirror assembly at a side ofa vehicle equipped with said imaging system; wherein, when said imagingarray sensor is disposed at least partially within the exterior rearviewmirror assembly, said imaging array sensor has a field of view exteriorof the equipped vehicle, and wherein said imaging array sensor isoperable to capture an image exterior of the equipped vehicle; a controlfor processing said captured image; wherein said control is operable todetermine that said imaging array sensor is misaligned when said imagingarray sensor is disposed at least partially within the exterior rearviewmirror assembly at the side of the equipped vehicle; and wherein saidcontrol, responsive to a determination of misalignment of said imagingarray sensor, is operable to adjust processing of said captured image toat least partially compensate for the determined misalignment of saidimaging array sensor.
 42. The imaging system of claim 41, wherein saidfield of view of said imaging array sensor encompasses at least one of(a) a rearward field of view exterior of the equipped vehicle, (b) asideward field of view exterior of the equipped vehicle and (c) aforward field of view exterior of the equipped vehicle.
 43. The imagingsystem of claim 41, wherein said control is operable to determine thatsaid imaging array sensor is aligned within a desired tolerance whensaid imaging array sensor is disposed at least partially within theexterior rearview mirror assembly at the side of the equipped vehicle.44. An imaging system for a vehicle, said imaging system comprising: animaging array sensor comprising a plurality of photo-sensing pixels,wherein said imaging array sensor is disposed at least partially withinan exterior rearview mirror assembly at a side of a vehicle equippedwith said imaging system; wherein, when said imaging array sensor isdisposed at least partially within the exterior rearview mirrorassembly, said imaging array sensor has a field of view exterior of theequipped vehicle, and wherein said imaging array sensor is operable tocapture an image exterior of the equipped vehicle; a control forprocessing said captured image; wherein said control is operable todetermine that said imaging array sensor is misaligned when said imagingarray sensor is disposed at least partially within the exterior rearviewmirror assembly at the side of the equipped vehicle; and wherein saidcaptured image comprises data and wherein said control, responsive to adetermination of misalignment of said imaging array sensor, is operableto adjust said data to at least partially compensate for the determinedmisalignment of said imaging array sensor.
 45. The imaging system ofclaim 44, wherein said field of view of said imaging array sensorencompasses at least one of (a) a rearward field of view exterior of theequipped vehicle, (b) a sideward field of view exterior of the equippedvehicle and (c) a forward field of view exterior of the equippedvehicle.
 46. The imaging system of claim 44, wherein said control isoperable to determine that said imaging array sensor is aligned within adesired tolerance when said imaging array sensor is disposed at leastpartially within the exterior rearview mirror assembly at the side ofthe equipped vehicle.
 47. An imaging system for a vehicle, said imagingsystem comprising: an imaging array sensor comprising a plurality ofphoto-sensing pixels, wherein said imaging array sensor is disposed atleast partially within an exterior rearview mirror assembly at a side ofa vehicle equipped with said imaging system; wherein, when said imagingarray sensor is disposed at least partially within the exterior rearviewmirror assembly, said imaging array sensor has a field of view exteriorof the equipped vehicle, and wherein said imaging array sensor isoperable to capture an image exterior of the equipped vehicle, andwherein said imaging array sensor has a field of view that encompasses aportion of the side of the equipped vehicle at which said imaging arraysensor is disposed; a control for processing said captured image;wherein said control is operable to determine that said imaging arraysensor is misaligned when said imaging array sensor is disposed at leastpartially within the exterior rearview mirror assembly at the side ofthe equipped vehicle; and wherein said control, responsive to adetermination of misalignment of said imaging array sensor, is operableto at least partially compensate for the determined misalignment of saidimaging array sensor, and wherein processing undertaken by said controlat least partially, accounts for misalignment of said imaging arraysensor at the side of the equipped vehicle at least in part responsiveto image data captured of the portion of the side of the equippedvehicle encompassed by said field of view of said imaging array sensor.48. The imaging system of claim 47, wherein said field of view of saidimaging array sensor encompasses at least one of (a) a rearward field ofview exterior of the equipped vehicle, (b) a sideward field of viewexterior of the equipped vehicle and (c) a forward field of viewexterior of the equipped vehicle.
 49. The imaging system of claim 47,wherein said control is operable to determine that said imaging arraysensor is aligned within a desired tolerance when said imaging arraysensor is disposed at least partially within the exterior rearviewmirror assembly at the side of the equipped vehicle.
 50. The imagingsystem of claim 47, wherein said field of view encompasses a structureat the side of the vehicle at which said imaging array sensor isdisposed.